/*
 * Copyright 2013 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Text;

using ZXing.Common;
using ZXing.PDF417.Internal.EC;

namespace ZXing.PDF417.Internal
{
   /// <summary>
   /// 
   /// </summary>
   /// <author>Guenther Grau</author>
   public static class PDF417ScanningDecoder
   {
      private const int CODEWORD_SKEW_SIZE = 2;

      private const int MAX_ERRORS = 3;
      private const int MAX_EC_CODEWORDS = 512;
      private static readonly ErrorCorrection errorCorrection = new ErrorCorrection();

      /// <summary>
      /// Decode the specified image, imageTopLeft, imageBottomLeft, imageTopRight, imageBottomRight, minCodewordWidth
      /// and maxCodewordWidth.
      /// TODO: don't pass in minCodewordWidth and maxCodewordWidth, pass in barcode columns for start and stop pattern
      /// columns. That way width can be deducted from the pattern column.
      /// This approach also allows to detect more details about the barcode, e.g. if a bar type (white or black) is wider 
      /// than it should be. This can happen if the scanner used a bad blackpoint.
      /// </summary>
      /// <param name="image">Image.</param>
      /// <param name="imageTopLeft">Image top left.</param>
      /// <param name="imageBottomLeft">Image bottom left.</param>
      /// <param name="imageTopRight">Image top right.</param>
      /// <param name="imageBottomRight">Image bottom right.</param>
      /// <param name="minCodewordWidth">Minimum codeword width.</param>
      /// <param name="maxCodewordWidth">Max codeword width.</param>
      public static DecoderResult decode(BitMatrix image,
                                         ResultPoint imageTopLeft,
                                         ResultPoint imageBottomLeft,
                                         ResultPoint imageTopRight,
                                         ResultPoint imageBottomRight,
                                         int minCodewordWidth,
                                         int maxCodewordWidth)
      {
         BoundingBox boundingBox = BoundingBox.Create(image, imageTopLeft, imageBottomLeft, imageTopRight, imageBottomRight);
         if (boundingBox == null)
            return null;

         DetectionResultRowIndicatorColumn leftRowIndicatorColumn = null;
         DetectionResultRowIndicatorColumn rightRowIndicatorColumn = null;
         DetectionResult detectionResult = null;
         for (int i = 0; i < 2; i++)
         {
            if (imageTopLeft != null)
            {
               leftRowIndicatorColumn = getRowIndicatorColumn(image, boundingBox, imageTopLeft, true, minCodewordWidth, maxCodewordWidth);
            }
            if (imageTopRight != null)
            {
               rightRowIndicatorColumn = getRowIndicatorColumn(image, boundingBox, imageTopRight, false, minCodewordWidth, maxCodewordWidth);
            }
            detectionResult = merge(leftRowIndicatorColumn, rightRowIndicatorColumn);
            if (detectionResult == null)
            {
               // TODO Based on Owen's Comments in <see cref="ZXing.ReaderException"/>, this method has been modified to continue silently
               // if a barcode was not decoded where it was detected instead of throwing a new exception object.
               return null;
            }
            if (i == 0 && detectionResult.Box != null &&
                (detectionResult.Box.MinY < boundingBox.MinY || detectionResult.Box.MaxY > boundingBox.MaxY))
            {
               boundingBox = detectionResult.Box;
            }
            else
            {
               detectionResult.Box = boundingBox;
               break;
            }
         }
         int maxBarcodeColumn = detectionResult.ColumnCount + 1;
         detectionResult.DetectionResultColumns[0] = leftRowIndicatorColumn;

         detectionResult.DetectionResultColumns[maxBarcodeColumn] = rightRowIndicatorColumn;

         bool leftToRight = leftRowIndicatorColumn != null;
         for (int barcodeColumnCount = 1; barcodeColumnCount <= maxBarcodeColumn; barcodeColumnCount++)
         {
            int barcodeColumn = leftToRight ? barcodeColumnCount : maxBarcodeColumn - barcodeColumnCount;
            if (detectionResult.DetectionResultColumns[barcodeColumn] != null)
            {
               // This will be the case for the opposite row indicator column, which doesn't need to be decoded again.
               continue;
            }
            DetectionResultColumn detectionResultColumn;
            if (barcodeColumn == 0 || barcodeColumn == maxBarcodeColumn)
            {
               detectionResultColumn = new DetectionResultRowIndicatorColumn(boundingBox, barcodeColumn == 0);
            }
            else
            {
               detectionResultColumn = new DetectionResultColumn(boundingBox);
            }
            detectionResult.DetectionResultColumns[barcodeColumn] = detectionResultColumn;
            int startColumn = -1;
            int previousStartColumn = startColumn;
            // TODO start at a row for which we know the start position, then detect upwards and downwards from there.
            for (int imageRow = boundingBox.MinY; imageRow <= boundingBox.MaxY; imageRow++)
            {
               startColumn = getStartColumn(detectionResult, barcodeColumn, imageRow, leftToRight);
               if (startColumn < 0 || startColumn > boundingBox.MaxX)
               {
                  if (previousStartColumn == -1)
                  {
                     continue;
                  }
                  startColumn = previousStartColumn;
               }
               Codeword codeword = detectCodeword(image, boundingBox.MinX, boundingBox.MaxX, leftToRight,
                                                  startColumn, imageRow, minCodewordWidth, maxCodewordWidth);
               if (codeword != null)
               {
                  detectionResultColumn.setCodeword(imageRow, codeword);
                  previousStartColumn = startColumn;
                  minCodewordWidth = Math.Min(minCodewordWidth, codeword.Width);
                  maxCodewordWidth = Math.Max(maxCodewordWidth, codeword.Width);
               }
            }
         }
         return createDecoderResult(detectionResult);
      }

      /// <summary>
      /// Merge the specified leftRowIndicatorColumn and rightRowIndicatorColumn.
      /// </summary>
      /// <param name="leftRowIndicatorColumn">Left row indicator column.</param>
      /// <param name="rightRowIndicatorColumn">Right row indicator column.</param>
      private static DetectionResult merge(DetectionResultRowIndicatorColumn leftRowIndicatorColumn,
                                           DetectionResultRowIndicatorColumn rightRowIndicatorColumn)
      {
         if (leftRowIndicatorColumn == null && rightRowIndicatorColumn == null)
         {
            return null;
         }
         BarcodeMetadata barcodeMetadata = getBarcodeMetadata(leftRowIndicatorColumn, rightRowIndicatorColumn);
         if (barcodeMetadata == null)
         {
            return null;
         }
         BoundingBox boundingBox = BoundingBox.merge(adjustBoundingBox(leftRowIndicatorColumn),
                                                     adjustBoundingBox(rightRowIndicatorColumn));

         return new DetectionResult(barcodeMetadata, boundingBox);
      }

      /// <summary>
      /// Adjusts the bounding box.
      /// </summary>
      /// <returns>The bounding box.</returns>
      /// <param name="rowIndicatorColumn">Row indicator column.</param>
      private static BoundingBox adjustBoundingBox(DetectionResultRowIndicatorColumn rowIndicatorColumn)
      {
         if (rowIndicatorColumn == null)
         {
            return null;
         }
         int[] rowHeights = rowIndicatorColumn.getRowHeights();
         if (rowHeights == null)
         {
            return null;
         }
         int maxRowHeight = getMax(rowHeights);
         int missingStartRows = 0;
         foreach (int rowHeight in rowHeights)
         {
            missingStartRows += maxRowHeight - rowHeight;
            if (rowHeight > 0)
            {
               break;
            }
         }
         Codeword[] codewords = rowIndicatorColumn.Codewords;
         for (int row = 0; missingStartRows > 0 && codewords[row] == null; row++)
         {
            missingStartRows--;
         }
         int missingEndRows = 0;
         for (int row = rowHeights.Length - 1; row >= 0; row--)
         {
            missingEndRows += maxRowHeight - rowHeights[row];
            if (rowHeights[row] > 0)
            {
               break;
            }
         }
         for (int row = codewords.Length - 1; missingEndRows > 0 && codewords[row] == null; row--)
         {
            missingEndRows--;
         }
         return rowIndicatorColumn.Box.addMissingRows(missingStartRows, missingEndRows, rowIndicatorColumn.IsLeft);
      }

      private static int getMax(int[] values)
      {
         int maxValue = -1;
         for (var index = values.Length - 1; index >= 0; index--)
         {
            maxValue = Math.Max(maxValue, values[index]);
         }
         return maxValue;
      }

      /// <summary>
      /// Gets the barcode metadata.
      /// </summary>
      /// <returns>The barcode metadata.</returns>
      /// <param name="leftRowIndicatorColumn">Left row indicator column.</param>
      /// <param name="rightRowIndicatorColumn">Right row indicator column.</param>
      private static BarcodeMetadata getBarcodeMetadata(DetectionResultRowIndicatorColumn leftRowIndicatorColumn,
                                                        DetectionResultRowIndicatorColumn rightRowIndicatorColumn)
      {

         BarcodeMetadata leftBarcodeMetadata;
         if (leftRowIndicatorColumn == null ||
             (leftBarcodeMetadata = leftRowIndicatorColumn.getBarcodeMetadata()) == null)
         {
            return rightRowIndicatorColumn == null ? null : rightRowIndicatorColumn.getBarcodeMetadata();
         }
         BarcodeMetadata rightBarcodeMetadata;
         if (rightRowIndicatorColumn == null ||
             (rightBarcodeMetadata = rightRowIndicatorColumn.getBarcodeMetadata()) == null)
         {
            return leftBarcodeMetadata;
         }

         if (leftBarcodeMetadata.ColumnCount != rightBarcodeMetadata.ColumnCount &&
             leftBarcodeMetadata.ErrorCorrectionLevel != rightBarcodeMetadata.ErrorCorrectionLevel &&
             leftBarcodeMetadata.RowCount != rightBarcodeMetadata.RowCount)
         {
            return null;
         }
         return leftBarcodeMetadata;
      }

      /// <summary>
      /// Gets the row indicator column.
      /// </summary>
      /// <returns>The row indicator column.</returns>
      /// <param name="image">Image.</param>
      /// <param name="boundingBox">Bounding box.</param>
      /// <param name="startPoint">Start point.</param>
      /// <param name="leftToRight">If set to <c>true</c> left to right.</param>
      /// <param name="minCodewordWidth">Minimum codeword width.</param>
      /// <param name="maxCodewordWidth">Max codeword width.</param>
      private static DetectionResultRowIndicatorColumn getRowIndicatorColumn(BitMatrix image,
                                                                             BoundingBox boundingBox,
                                                                             ResultPoint startPoint,
                                                                             bool leftToRight,
                                                                             int minCodewordWidth,
                                                                             int maxCodewordWidth)
      {
         DetectionResultRowIndicatorColumn rowIndicatorColumn = new DetectionResultRowIndicatorColumn(boundingBox, leftToRight);
         for (int i = 0; i < 2; i++)
         {
            int increment = i == 0 ? 1 : -1;
            int startColumn = (int) startPoint.X;
            for (int imageRow = (int) startPoint.Y; imageRow <= boundingBox.MaxY &&
                                                    imageRow >= boundingBox.MinY; imageRow += increment)
            {
               Codeword codeword = detectCodeword(image, 0, image.Width, leftToRight, startColumn, imageRow,
                                                  minCodewordWidth, maxCodewordWidth);
               if (codeword != null)
               {
                  rowIndicatorColumn.setCodeword(imageRow, codeword);
                  if (leftToRight)
                  {
                     startColumn = codeword.StartX;
                  }
                  else
                  {
                     startColumn = codeword.EndX;
                  }
               }
            }
         }
         return rowIndicatorColumn;
      }

      /// <summary>
      /// Adjusts the codeword count.
      /// </summary>
      /// <param name="detectionResult">Detection result.</param>
      /// <param name="barcodeMatrix">Barcode matrix.</param>
      private static bool adjustCodewordCount(DetectionResult detectionResult, BarcodeValue[][] barcodeMatrix)
      {
         int[] numberOfCodewords = barcodeMatrix[0][1].getValue();
         int calculatedNumberOfCodewords = detectionResult.ColumnCount*
                                           detectionResult.RowCount -
                                           getNumberOfECCodeWords(detectionResult.ErrorCorrectionLevel);
         if (numberOfCodewords.Length == 0)
         {
            if (calculatedNumberOfCodewords < 1 || calculatedNumberOfCodewords > PDF417Common.MAX_CODEWORDS_IN_BARCODE)
            {
               return false;
            }
            barcodeMatrix[0][1].setValue(calculatedNumberOfCodewords);
         }
         else if (numberOfCodewords[0] != calculatedNumberOfCodewords)
         {
            // The calculated one is more reliable as it is derived from the row indicator columns
            barcodeMatrix[0][1].setValue(calculatedNumberOfCodewords);
         }

         return true;
      }

      /// <summary>
      /// Creates the decoder result.
      /// </summary>
      /// <returns>The decoder result.</returns>
      /// <param name="detectionResult">Detection result.</param>
      private static DecoderResult createDecoderResult(DetectionResult detectionResult)
      {
         BarcodeValue[][] barcodeMatrix = createBarcodeMatrix(detectionResult);
         if (barcodeMatrix == null)
            return null;

         if (!adjustCodewordCount(detectionResult, barcodeMatrix))
         {
            return null;
         }
         List<int> erasures = new List<int>();
         int[] codewords = new int[detectionResult.RowCount*detectionResult.ColumnCount];
         List<int[]> ambiguousIndexValuesList = new List<int[]>();
         List<int> ambiguousIndexesList = new List<int>();
         for (int row = 0; row < detectionResult.RowCount; row++)
         {
            for (int column = 0; column < detectionResult.ColumnCount; column++)
            {
               int[] values = barcodeMatrix[row][column + 1].getValue();
               int codewordIndex = row*detectionResult.ColumnCount + column;
               if (values.Length == 0)
               {
                  erasures.Add(codewordIndex);
               }
               else if (values.Length == 1)
               {
                  codewords[codewordIndex] = values[0];
               }
               else
               {
                  ambiguousIndexesList.Add(codewordIndex);
                  ambiguousIndexValuesList.Add(values);
               }
            }
         }
         int[][] ambiguousIndexValues = new int[ambiguousIndexValuesList.Count][];
         for (int i = 0; i < ambiguousIndexValues.Length; i++)
         {
            ambiguousIndexValues[i] = ambiguousIndexValuesList[i];
         }
         return createDecoderResultFromAmbiguousValues(detectionResult.ErrorCorrectionLevel, codewords,
                                                       erasures.ToArray(), ambiguousIndexesList.ToArray(), ambiguousIndexValues);
      }

      /// <summary>
      /// This method deals with the fact, that the decoding process doesn't always yield a single most likely value. The
      /// current error correction implementation doesn't deal with erasures very well, so it's better to provide a value
      /// for these ambiguous codewords instead of treating it as an erasure. The problem is that we don't know which of
      /// the ambiguous values to choose. We try decode using the first value, and if that fails, we use another of the
      /// ambiguous values and try to decode again. This usually only happens on very hard to read and decode barcodes,
      /// so decoding the normal barcodes is not affected by this.
      /// </summary>
      /// <returns>The decoder result from ambiguous values.</returns>
      /// <param name="ecLevel">Ec level.</param>
      /// <param name="codewords">Codewords.</param>
      /// <param name="erasureArray">contains the indexes of erasures.</param>
      /// <param name="ambiguousIndexes">array with the indexes that have more than one most likely value.</param>
      /// <param name="ambiguousIndexValues">two dimensional array that contains the ambiguous values. The first dimension must
      /// be the same Length as the ambiguousIndexes array.</param>
      private static DecoderResult createDecoderResultFromAmbiguousValues(int ecLevel,
                                                                          int[] codewords,
                                                                          int[] erasureArray,
                                                                          int[] ambiguousIndexes,
                                                                          int[][] ambiguousIndexValues)
      {
         int[] ambiguousIndexCount = new int[ambiguousIndexes.Length];

         int tries = 100;
         while (tries-- > 0)
         {
            for (int i = 0; i < ambiguousIndexCount.Length; i++)
            {
               codewords[ambiguousIndexes[i]] = ambiguousIndexValues[i][ambiguousIndexCount[i]];
            }
            try
            {
               var result = decodeCodewords(codewords, ecLevel, erasureArray);
               if (result != null)
                  return result;
            }
            catch (ReaderException)
            {
               // ignored, should not happen
            }
            if (ambiguousIndexCount.Length == 0)
            {
               return null;
            }
            for (int i = 0; i < ambiguousIndexCount.Length; i++)
            {
               if (ambiguousIndexCount[i] < ambiguousIndexValues[i].Length - 1)
               {
                  ambiguousIndexCount[i]++;
                  break;
               }
               else
               {
                  ambiguousIndexCount[i] = 0;
                  if (i == ambiguousIndexCount.Length - 1)
                  {
                     return null;
                  }
               }
            }
         }
         return null;
      }

      /// <summary>
      /// Creates the barcode matrix.
      /// </summary>
      /// <returns>The barcode matrix.</returns>
      /// <param name="detectionResult">Detection result.</param>
      private static BarcodeValue[][] createBarcodeMatrix(DetectionResult detectionResult)
      {
         // Manually setup Jagged Array in C#
         var barcodeMatrix = new BarcodeValue[detectionResult.RowCount][];
         for (int row = 0; row < barcodeMatrix.Length; row++)
         {
            barcodeMatrix[row] = new BarcodeValue[detectionResult.ColumnCount + 2];
            for (int col = 0; col < barcodeMatrix[row].Length; col++)
            {
               barcodeMatrix[row][col] = new BarcodeValue();
            }
         }

         int column = 0;
         foreach (DetectionResultColumn detectionResultColumn in detectionResult.getDetectionResultColumns())
         {
            if (detectionResultColumn != null)
            {
               foreach (Codeword codeword in detectionResultColumn.Codewords)
               {
                  if (codeword != null)
                  {
                     int rowNumber = codeword.RowNumber;
                     if (rowNumber >= 0)
                     {
                        if (rowNumber >= barcodeMatrix.Length)
                        {
                           return null;
                        }
                        barcodeMatrix[rowNumber][column].setValue(codeword.Value);
                     }
                  }
               }
            }
            column++;
         }

         return barcodeMatrix;
      }

      /// <summary>
      /// Tests to see if the Barcode Column is Valid
      /// </summary>
      /// <returns><c>true</c>, if barcode column is valid, <c>false</c> otherwise.</returns>
      /// <param name="detectionResult">Detection result.</param>
      /// <param name="barcodeColumn">Barcode column.</param>
      private static bool isValidBarcodeColumn(DetectionResult detectionResult, int barcodeColumn)
      {
         return (barcodeColumn >= 0) && (barcodeColumn < detectionResult.DetectionResultColumns.Length);
      }

      /// <summary>
      /// Gets the start column.
      /// </summary>
      /// <returns>The start column.</returns>
      /// <param name="detectionResult">Detection result.</param>
      /// <param name="barcodeColumn">Barcode column.</param>
      /// <param name="imageRow">Image row.</param>
      /// <param name="leftToRight">If set to <c>true</c> left to right.</param>
      private static int getStartColumn(DetectionResult detectionResult,
                                        int barcodeColumn,
                                        int imageRow,
                                        bool leftToRight)
      {
         int offset = leftToRight ? 1 : -1;
         Codeword codeword = null;
         if (isValidBarcodeColumn(detectionResult, barcodeColumn - offset))
         {
            codeword = detectionResult.DetectionResultColumns[barcodeColumn - offset].getCodeword(imageRow);
         }
         if (codeword != null)
         {
            return leftToRight ? codeword.EndX : codeword.StartX;
         }
         codeword = detectionResult.DetectionResultColumns[barcodeColumn].getCodewordNearby(imageRow);
         if (codeword != null)
         {
            return leftToRight ? codeword.StartX : codeword.EndX;
         }
         if (isValidBarcodeColumn(detectionResult, barcodeColumn - offset))
         {
            codeword = detectionResult.DetectionResultColumns[barcodeColumn - offset].getCodewordNearby(imageRow);
         }
         if (codeword != null)
         {
            return leftToRight ? codeword.EndX : codeword.StartX;
         }
         int skippedColumns = 0;

         while (isValidBarcodeColumn(detectionResult, barcodeColumn - offset))
         {
            barcodeColumn -= offset;
            foreach (Codeword previousRowCodeword in detectionResult.DetectionResultColumns[barcodeColumn].Codewords)
            {
               if (previousRowCodeword != null)
               {
                  return (leftToRight ? previousRowCodeword.EndX : previousRowCodeword.StartX) +
                         offset*
                         skippedColumns*
                         (previousRowCodeword.EndX - previousRowCodeword.StartX);
               }
            }
            skippedColumns++;
         }
         return leftToRight ? detectionResult.Box.MinX : detectionResult.Box.MaxX;
      }

      /// <summary>
      /// Detects the codeword.
      /// </summary>
      /// <returns>The codeword.</returns>
      /// <param name="image">Image.</param>
      /// <param name="minColumn">Minimum column.</param>
      /// <param name="maxColumn">Max column.</param>
      /// <param name="leftToRight">If set to <c>true</c> left to right.</param>
      /// <param name="startColumn">Start column.</param>
      /// <param name="imageRow">Image row.</param>
      /// <param name="minCodewordWidth">Minimum codeword width.</param>
      /// <param name="maxCodewordWidth">Max codeword width.</param>
      private static Codeword detectCodeword(BitMatrix image,
                                             int minColumn,
                                             int maxColumn,
                                             bool leftToRight,
                                             int startColumn,
                                             int imageRow,
                                             int minCodewordWidth,
                                             int maxCodewordWidth)
      {
         startColumn = adjustCodewordStartColumn(image, minColumn, maxColumn, leftToRight, startColumn, imageRow);
         // we usually know fairly exact now how long a codeword is. We should provide minimum and maximum expected length
         // and try to adjust the read pixels, e.g. remove single pixel errors or try to cut off exceeding pixels.
         // min and maxCodewordWidth should not be used as they are calculated for the whole barcode an can be inaccurate
         // for the current position
         int[] moduleBitCount = getModuleBitCount(image, minColumn, maxColumn, leftToRight, startColumn, imageRow);
         if (moduleBitCount == null)
         {
            return null;
         }
         int endColumn;
         int codewordBitCount = PDF417Common.getBitCountSum(moduleBitCount);
         if (leftToRight)
         {
            endColumn = startColumn + codewordBitCount;
         }
         else
         {
            for (int i = 0; i < (moduleBitCount.Length >> 1); i++)
            {
               int tmpCount = moduleBitCount[i];
               moduleBitCount[i] = moduleBitCount[moduleBitCount.Length - 1 - i];
               moduleBitCount[moduleBitCount.Length - 1 - i] = tmpCount;
            }
            endColumn = startColumn;
            startColumn = endColumn - codewordBitCount;
         }
         // TODO implement check for width and correction of black and white bars
         // use start (and maybe stop pattern) to determine if blackbars are wider than white bars. If so, adjust.
         // should probably done only for codewords with a lot more than 17 bits. 
         // The following fixes 10-1.png, which has wide black bars and small white bars
         //    for (int i = 0; i < moduleBitCount.Length; i++) {
         //      if (i % 2 == 0) {
         //        moduleBitCount[i]--;
         //      } else {
         //        moduleBitCount[i]++;
         //      }
         //    }

         // We could also use the width of surrounding codewords for more accurate results, but this seems
         // sufficient for now
         if (!checkCodewordSkew(codewordBitCount, minCodewordWidth, maxCodewordWidth))
         {
            // We could try to use the startX and endX position of the codeword in the same column in the previous row,
            // create the bit count from it and normalize it to 8. This would help with single pixel errors.
            return null;
         }

         int decodedValue = PDF417CodewordDecoder.getDecodedValue(moduleBitCount);
         int codeword = PDF417Common.getCodeword(decodedValue);
         if (codeword == -1)
         {
            return null;
         }
         return new Codeword(startColumn, endColumn, getCodewordBucketNumber(decodedValue), codeword);
      }

      /// <summary>
      /// Gets the module bit count.
      /// </summary>
      /// <returns>The module bit count.</returns>
      /// <param name="image">Image.</param>
      /// <param name="minColumn">Minimum column.</param>
      /// <param name="maxColumn">Max column.</param>
      /// <param name="leftToRight">If set to <c>true</c> left to right.</param>
      /// <param name="startColumn">Start column.</param>
      /// <param name="imageRow">Image row.</param>
      private static int[] getModuleBitCount(BitMatrix image,
                                             int minColumn,
                                             int maxColumn,
                                             bool leftToRight,
                                             int startColumn,
                                             int imageRow)
      {
         int imageColumn = startColumn;
         int[] moduleBitCount = new int[8];
         int moduleNumber = 0;
         int increment = leftToRight ? 1 : -1;
         bool previousPixelValue = leftToRight;
         while (((leftToRight && imageColumn < maxColumn) || (!leftToRight && imageColumn >= minColumn)) &&
                moduleNumber < moduleBitCount.Length)
         {
            if (image[imageColumn, imageRow] == previousPixelValue)
            {
               moduleBitCount[moduleNumber]++;
               imageColumn += increment;
            }
            else
            {
               moduleNumber++;
               previousPixelValue = !previousPixelValue;
            }
         }
         if (moduleNumber == moduleBitCount.Length ||
             (((leftToRight && imageColumn == maxColumn) || (!leftToRight && imageColumn == minColumn)) && moduleNumber == moduleBitCount.Length - 1))
         {
            return moduleBitCount;
         }
         return null;
      }

      /// <summary>
      /// Gets the number of EC code words.
      /// </summary>
      /// <returns>The number of EC code words.</returns>
      /// <param name="barcodeECLevel">Barcode EC level.</param>
      private static int getNumberOfECCodeWords(int barcodeECLevel)
      {
         return 2 << barcodeECLevel;
      }

      /// <summary>
      /// Adjusts the codeword start column.
      /// </summary>
      /// <returns>The codeword start column.</returns>
      /// <param name="image">Image.</param>
      /// <param name="minColumn">Minimum column.</param>
      /// <param name="maxColumn">Max column.</param>
      /// <param name="leftToRight">If set to <c>true</c> left to right.</param>
      /// <param name="codewordStartColumn">Codeword start column.</param>
      /// <param name="imageRow">Image row.</param>
      private static int adjustCodewordStartColumn(BitMatrix image,
                                                   int minColumn,
                                                   int maxColumn,
                                                   bool leftToRight,
                                                   int codewordStartColumn,
                                                   int imageRow)
      {
         int correctedStartColumn = codewordStartColumn;
         int increment = leftToRight ? -1 : 1;
         // there should be no black pixels before the start column. If there are, then we need to start earlier.
         for (int i = 0; i < 2; i++)
         {
            while (((leftToRight && correctedStartColumn >= minColumn) || (!leftToRight && correctedStartColumn < maxColumn)) &&
                   leftToRight == image[correctedStartColumn, imageRow])
            {
               if (Math.Abs(codewordStartColumn - correctedStartColumn) > CODEWORD_SKEW_SIZE)
               {
                  return codewordStartColumn;
               }
               correctedStartColumn += increment;
            }
            increment = -increment;
            leftToRight = !leftToRight;
         }
         return correctedStartColumn;
      }

      /// <summary>
      /// Checks the codeword for any skew.
      /// </summary>
      /// <returns><c>true</c>, if codeword is within the skew, <c>false</c> otherwise.</returns>
      /// <param name="codewordSize">Codeword size.</param>
      /// <param name="minCodewordWidth">Minimum codeword width.</param>
      /// <param name="maxCodewordWidth">Max codeword width.</param>
      private static bool checkCodewordSkew(int codewordSize, int minCodewordWidth, int maxCodewordWidth)
      {
         return minCodewordWidth - CODEWORD_SKEW_SIZE <= codewordSize &&
                codewordSize <= maxCodewordWidth + CODEWORD_SKEW_SIZE;
      }

      /// <summary>
      /// Decodes the codewords.
      /// </summary>
      /// <returns>The codewords.</returns>
      /// <param name="codewords">Codewords.</param>
      /// <param name="ecLevel">Ec level.</param>
      /// <param name="erasures">Erasures.</param>
      private static DecoderResult decodeCodewords(int[] codewords, int ecLevel, int[] erasures)
      {
         if (codewords.Length == 0)
         {
            return null;
         }

         int numECCodewords = 1 << (ecLevel + 1);

         int correctedErrorsCount = correctErrors(codewords, erasures, numECCodewords);
         if (correctedErrorsCount < 0)
         {
            return null;
         }
         if (!verifyCodewordCount(codewords, numECCodewords))
         {
            return null;
         }

         // Decode the codewords
         DecoderResult decoderResult = DecodedBitStreamParser.decode(codewords, ecLevel.ToString());
         if (decoderResult != null)
         {
            decoderResult.ErrorsCorrected = correctedErrorsCount;
            decoderResult.Erasures = erasures.Length;
         }
         return decoderResult;
      }

      /// <summary>
      /// Given data and error-correction codewords received, possibly corrupted by errors, attempts to
      /// correct the errors in-place.
      /// </summary>
      /// <returns>The errors.</returns>
      /// <param name="codewords">data and error correction codewords.</param>
      /// <param name="erasures">positions of any known erasures.</param>
      /// <param name="numECCodewords">number of error correction codewords that are available in codewords.</param>
      private static int correctErrors(int[] codewords, int[] erasures, int numECCodewords)
      {
         if (erasures != null &&
             erasures.Length > numECCodewords/2 + MAX_ERRORS ||
             numECCodewords < 0 ||
             numECCodewords > MAX_EC_CODEWORDS)
         {
            // Too many errors or EC Codewords is corrupted
            return -1;

         }
         int errorCount;
         if (!errorCorrection.decode(codewords, numECCodewords, erasures, out errorCount))
         {
            return -1;
         }
         return errorCount;
      }

      /// <summary>
      /// Verifies that all is well with the the codeword array.
      /// </summary>
      /// <param name="codewords">Codewords.</param>
      /// <param name="numECCodewords">Number EC codewords.</param>
      private static bool verifyCodewordCount(int[] codewords, int numECCodewords)
      {
         if (codewords.Length < 4)
         {
            // Codeword array size should be at least 4 allowing for
            // Count CW, At least one Data CW, Error Correction CW, Error Correction CW
            return false;
         }
         // The first codeword, the Symbol Length Descriptor, shall always encode the total number of data
         // codewords in the symbol, including the Symbol Length Descriptor itself, data codewords and pad
         // codewords, but excluding the number of error correction codewords.
         int numberOfCodewords = codewords[0];
         if (numberOfCodewords > codewords.Length)
         {
            return false;
         }
         if (numberOfCodewords == 0)
         {
            // Reset to the Length of the array - 8 (Allow for at least level 3 Error Correction (8 Error Codewords)
            if (numECCodewords < codewords.Length)
            {
               codewords[0] = codewords.Length - numECCodewords;
            }
            else
            {
               return false;
            }
         }

         return true;
      }

      /// <summary>
      /// Gets the bit count for codeword.
      /// </summary>
      /// <returns>The bit count for codeword.</returns>
      /// <param name="codeword">Codeword.</param>
      private static int[] getBitCountForCodeword(int codeword)
      {
         int[] result = new int[8];
         int previousValue = 0;
         int i = result.Length - 1;
         while (true)
         {
            if ((codeword & 0x1) != previousValue)
            {
               previousValue = codeword & 0x1;
               i--;
               if (i < 0)
               {
                  break;
               }
            }
            result[i]++;
            codeword >>= 1;
         }
         return result;
      }

      /// <summary>
      /// Gets the codeword bucket number.
      /// </summary>
      /// <returns>The codeword bucket number.</returns>
      /// <param name="codeword">Codeword.</param>
      private static int getCodewordBucketNumber(int codeword)
      {
         return getCodewordBucketNumber(getBitCountForCodeword(codeword));
      }

      /// <summary>
      /// Gets the codeword bucket number.
      /// </summary>
      /// <returns>The codeword bucket number.</returns>
      /// <param name="moduleBitCount">Module bit count.</param>
      private static int getCodewordBucketNumber(int[] moduleBitCount)
      {
         return (moduleBitCount[0] - moduleBitCount[2] + moduleBitCount[4] - moduleBitCount[6] + 9)%9;
      }

      /// <summary>
      /// Returns a <see cref="System.String"/> that represents the <see cref="ZXing.PDF417.Internal.BarcodeValue"/> jagged array.
      /// </summary>
      /// <returns>A <see cref="System.String"/> that represents the <see cref="ZXing.PDF417.Internal.BarcodeValue"/> jagged array.</returns>
      /// <param name="barcodeMatrix">Barcode matrix as a jagged array.</param>
      public static String ToString(BarcodeValue[][] barcodeMatrix)
      {
         StringBuilder formatter = new StringBuilder();
         for (int row = 0; row < barcodeMatrix.Length; row++)
         {
            formatter.AppendFormat(CultureInfo.InvariantCulture, "Row {0,2}: ", row);
            for (int column = 0; column < barcodeMatrix[row].Length; column++)
            {
               BarcodeValue barcodeValue = barcodeMatrix[row][column];
               int[] values = barcodeValue.getValue();
               if (values.Length == 0)
               {
                  formatter.Append("        ");
               }
               else
               {
                  formatter.AppendFormat(CultureInfo.InvariantCulture, "{0,4}({1,2})", values[0], barcodeValue.getConfidence(values[0]));
               }
            }
            formatter.Append("\n");
         }
         return formatter.ToString();
      }
   }
}